Many countries with nuclear power are investigating deep geological disposal as a method of long term disposal of spent nuclear fuel and high-level waste such as from medicinal applications. The development and implementation of waste management strategies based upon geological disposal is becoming a preferred option of hazardous waste disposal. Conventional methods of disposal typically include burying the radioactive waste in geological repositories to isolate the waste in sedimentary rocks clay, or salt; igneous rocks such as granite; or metamorphic rocks. Abandoned drilling shafts or other deep wells are used to store radioactive waste; however, such waste generates considerable heat which must be dissipated for long term storage, and the possibility of leakage of the waste and contamination of ground water must be taken into consideration in site selection.
The collapsible waste disposal container in the claimed invention provides for the permanent disposition of any unwanted waste material such as radioactive fuel residue from nuclear power plants by burying the waste disposal container and waste in the ocean sediment deep in the subduction zone between the tectonic plates of the earth's mantle. The collapsible container method of disposal utilizes the earth's natural geological characteristics and evolutionary development as a means of neutralizing the waste according to the method of disposal described herein.
The earth's rigid outer crust of rock and upper mantle, the lithosphere, consists of about twelve rigid plates approximately 30 to 60 miles thick which move relative to a softer plastic underlayer called the asthenosphere which extends downward toward the center of the earth for approximately 240 miles. The lithosphere and the asthenosphere make up the upper mantle of the earth. Below the asthenosphere is the mesosphere or deep mantle. The temperature of the deep mantle increases with the distance below the earth's surface, typically reaching about 1200 degrees centigrade at 100 kilometers below sea level.
The tectonic plates are in a continuous state of movement caused by the up-welling of magma at the plate boundaries in the mid-ocean ridges. The Mid-Atlantic Ridge extends roughly from Greenland mid-way between Europe and the North American continents and between Africa and South America to approximately the end of the South American continent. The up-welling along this ridge causes the North American plate and the Eurasian Plate to become larger pushing the American and European plates farther apart.
Since the Earth does not become larger in diameter, the question of what becomes of the excess material in the lithosphere was a puzzle. Scientists theorize that the old lithosphere is subducted (pushed down) into the earth's mantle. These subduction zones form deep oceanic trenches adjacent to the island arcs of the western Pacific and along the western coast of South America. It is an accepted premise that the Himalayan Mountains were formed by the subduction of the Indian plate under the Eurasian plate.
It is reported that the subduction rate at which a plate descends perpendicular to the arc of the earth's surface varies from 0.5 to 9.5 centimeters per year. The middle American subduction zone located just off the Pacific coast of Central America has the greatest subduction rate of 9.5 centimeters per year.
More detailed information concerning plate tectonic geology is available from several scientific periodicals including: Scientific American Magazine. "The Subduction of the Lithosphere", by M. Nafi Toksoz, November 1975; Scientific American Magazine, "Sea-floor spreading", by Don L. Anderson, November 1971; Scientific American Magazine, "Geosynclines, Mountains and Continent-building", by Robert S. Dietz, March 1972; Discover, "Simmering Planet", by Ingrid Wickelgren; Science News of the Week, "Deep-Sea Muds Hold Tight to Hot Elements" by R. Monastersky, Volume 138.
The oceanic subduction zones, especially in the Pacific Ocean are associated with deep trenches. For example, the Marianas trench was explored by the bathysphere to a depth of 30,000 feet. The Peru/Chile trench is about eight kilometers, approximately 4.8 miles, deep. At the bottom of these deep trenches are collections of sediment. The sediments may be several kilometers thick and in turn provide some lubrication between the lower surface of the continental plate and the upper surface of the subducting plate.
A waste disposal package must be designed which takes into consideration such factors as the type of waste for disposal, the geological medium, the hydrology of the site, and the regulatory requirements. The waste disposal package typically includes the container and any buffering material inside or outside of the container. The waste disposal container must provide for the safe handling of the waste during storage, transportation, and placement of the waste for long term containment. If the waste is disposed using conventional methods in 300 to 1200 feet deep mines or wells in rock formations, it is necessary to design the container taking into consideration the ability of the container to prevent the release of radionuclides; the container material degradation to the environment and waste; the environment surrounding the waste container; buffer materials; and the pressure and temperature of the surrounding environment.